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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 01 Jul 2015 (Wednesday) 21:43
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Sigma 50 Art focusing 70D vs 7dii

 
vengence
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Jul 01, 2015 21:43 |  #1

I ordered and received a Sigma 50 Art and it had completely inconsistent focusing on my 70D when focusing through the view finder (contrast AF). It is however, a simply stunningly amazing sharper than a razor lens when using DPAF. My use case for the lens is wide open using the view finder, so despite perfect focusing with DPAF, it's now how I'd use the lens. I was talked into by the vendor sending it back and exchanging it for another copy, though after reading forum posts I don't have much hope in this solving the issue. The forums seem to say it will either AF on a body or it won't. So my question is, will it AF significantly better on a 7D ii than it will a 70D? There are some upgrades (and some minues too) on the 7dii that I think I'd be willing to spend the money if I knew the 50 Art would focus flawlessly on. As an aside, the 50 Art that I just sent back, focused perfectly on a 6d of a friends.




  
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nighthawk82
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Jul 02, 2015 00:39 |  #2

There is a very hyped up thread of this problem with the 70D which affects some models. The symptom is exactly like you've seen, poor focussing through viewfinder, but good focussing through live view.

It seems your 70D might be affected by this issue.... have you tried with other fast lenses? Anything below f/2.8 is more likely to exhibit the issue.

Here you go, plenty of bedtime reading...
https://photography-on-the.net …read.php?t=1354​075&page=1


Dennis
Canon EOS 70D | Canon EOS 450D | Canon EF 135mm f/2L USM | Canon EF 100mm f/2.8 USM Macro | Canon EF 85mm f/1.8 USM | Canon EF 50mm f/1.4 USM | Canon EF 40mm f/2.8 STM | Canon EF-S 10-18mm f/4.5-5.6 IS STM | Canon EF-S 18-135mm f/3.5-5.6 IS STM | Canon EF-S 55-250mm f/4-5.6 IS II | Tamron SP AF 17-50mm f/2.8 XR Di II LD IF

  
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BigAl007
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Jul 02, 2015 02:46 |  #3

Just a note to the OP but I think you have your Contrast Detect Autofocus (CDAF) confused with your Phase Detect Autofocus (PDAF). When using the Optical Viewfinder, you are using the PDAF system, which although quick, as it knows how far and in what direction you are out of focus by in a single measurement, requires correct calibration to be accurate. On the otherhand, the CDAF system is used in Liveview mode, this is much slower, as it requires repeated measurements of the contrast coming from the image feed from the actual sensor. As it uses the actual sensor to make its measurements it doesn't need the same level of calibration of the whole system. As long as it truly has reached the point of maximum contrast, the image MUST be in focus.

The 70D and also the 7DII both have a hybrid CDAF/PDAF system built into the sensor. This allows for good AF while in video mode, as it supposedly reduces the amount of hunting for optimum focus that the CDAF system has to do. As I have niether of these two cameras I cannot comment on how effective this system might be.

Alan


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vengence
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Jul 03, 2015 09:40 |  #4

nighthawk82 wrote in post #17617695 (external link)
There is a very hyped up thread of this problem with the 70D which affects some models. The symptom is exactly like you've seen, poor focussing through viewfinder, but good focussing through live view.

It seems your 70D might be affected by this issue.... have you tried with other fast lenses? Anything below f/2.8 is more likely to exhibit the issue.

Here you go, plenty of bedtime reading...
https://photography-on-the.net …read.php?t=1354​075&page=1

I had and recently sold a 50 f/1.4, but never carefully checked for the problem, but I thought I had successfully calibrated it in the past. I've got several f/2.8 lens but have never noticed a problem with them, but the depth of field on a crop at f/2.8 on a reasonably subject is more than large enough to hide flaws that'd be exposed by at 1.4 Unfortunately, this whole mess is giving me a bit of a crisis of confidence. I have started going through that other thread, hyped up is right. Do the people in it ever come to a conclusion that there is a problem and has canon offered a solution? I'm tempted to go buy a 50 f/1.8 STM for 125$ and compare it with the Art. If it's a problem with my body, it should show up on both lenses and if it's a problem with the Art it'll only show up on the Art, right? Actually, I'm pretty damn sure this is what I'm going to do because it should be a very easy test to see if I have a problem or not.




  
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vengence
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Post edited over 3 years ago by vengence.
     
Jul 03, 2015 09:41 |  #5

BigAl007 wrote in post #17617755 (external link)
Just a note to the OP but I think you have your Contrast Detect Autofocus (CDAF) confused with your Phase Detect Autofocus (PDAF). When using the Optical Viewfinder, you are using the PDAF system, which although quick, as it knows how far and in what direction you are out of focus by in a single measurement, requires correct calibration to be accurate. On the otherhand, the CDAF system is used in Liveview mode, this is much slower, as it requires repeated measurements of the contrast coming from the image feed from the actual sensor. As it uses the actual sensor to make its measurements it doesn't need the same level of calibration of the whole system. As long as it truly has reached the point of maximum contrast, the image MUST be in focus.

The 70D and also the 7DII both have a hybrid CDAF/PDAF system built into the sensor. This allows for good AF while in video mode, as it supposedly reduces the amount of hunting for optimum focus that the CDAF system has to do. As I have niether of these two cameras I cannot comment on how effective this system might be.

Alan

Yeah, I said it wrong. Thanks for the correction, was a bit tired when I wrote that.




  
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mwsilver
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Jul 05, 2015 00:21 |  #6

vengence wrote in post #17619079 (external link)
I had and recently sold a 50 f/1.4, but never carefully checked for the problem, but I thought I had successfully calibrated it in the past. I've got several f/2.8 lens but have never noticed a problem with them, but the depth of field on a crop at f/2.8 on a reasonably subject is more than large enough to hide flaws that'd be exposed by at 1.4 Unfortunately, this whole mess is giving me a bit of a crisis of confidence. I have started going through that other thread, hyped up is right. Do the people in it ever come to a conclusion that there is a problem and has canon offered a solution? I'm tempted to go buy a 50 f/1.8 STM for 125$ and compare it with the Art. If it's a problem with my body, it should show up on both lenses and if it's a problem with the Art it'll only show up on the Art, right? Actually, I'm pretty damn sure this is what I'm going to do because it should be a very easy test to see if I have a problem or not.

Attaching the same lens to two different camera bodies will not give you two identical results. The Sigma 18-35mm works very well on my 60D but is way off on the 7D2. The Canon 35mm f/2 IS works better and more consistently on the 7D2 than on my 60D. You could mount the same Sigma 50mm f/1.4 on several different bodies and get slightly different results, even on different copies of the same body. Even with tight tolerances, there is often slight lens to lens and camera to camera variability. That why camera bodies have micro focus adjustment capabilities. I have 4 Canon bodies, My two sigma lenses work a little differently on each of them.


Mark
Canon 7D2, 60D, T3i, T2i, Sigma 18-35 f/1.8, 30 f/1.4. Canon EF 70-200 L f/4 IS, EF 35 f/2 IS, EFs 10-18 STM, EFs 15-85, EFs 18-200, EF 50 f/1.8 STM, Tamron 18-270 PZD, B+W MRC CPL, Canon 320EX, Vanguard Alta Pro 254CT & SBH 250 head. RODE Stereo Videomic Pro, DXO PhotoLab, Elements 15

  
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nighthawk82
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Jul 05, 2015 03:33 as a reply to  @ vengence's post |  #7

Personally I would first try to borrow some fast lenses from friends and try the viewfinder vs live view. We all know this was/is an issue on some 70D models so it makes sense to investigate it first to see if your camera is affected.

As to whether Canon will repair it. It seems that they have a bad habit of returning the camera with the exact same problem, but perseverance and possibly even sample photos of live view vs viewfinder might convince them to replace the camera. Might be a bit of a battle though before they budge.


Dennis
Canon EOS 70D | Canon EOS 450D | Canon EF 135mm f/2L USM | Canon EF 100mm f/2.8 USM Macro | Canon EF 85mm f/1.8 USM | Canon EF 50mm f/1.4 USM | Canon EF 40mm f/2.8 STM | Canon EF-S 10-18mm f/4.5-5.6 IS STM | Canon EF-S 18-135mm f/3.5-5.6 IS STM | Canon EF-S 55-250mm f/4-5.6 IS II | Tamron SP AF 17-50mm f/2.8 XR Di II LD IF

  
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vengence
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Jul 05, 2015 07:55 |  #8

mwsilver wrote in post #17620978 (external link)
Attaching the same lens to two different camera bodies will not give you two identical results. The Sigma 18-35mm works very well on my 60D but is way off on the 7D2. The Canon 35mm f/2 IS works better and more consistently on the 7D2 than on my 60D. You could mount the same Sigma 50mm f/1.4 on several different bodies and get slightly different results, even on different copies of the same body. Even with tight tolerances, there is often slight lens to lens and camera to camera variability. That why camera bodies have micro focus adjustment capabilities. I have 4 Canon bodies, My two sigma lenses work a little differently on each of them.

I'm not talking about a simple repeatable offset, if that existed I'd simply put in the MFA needed and be done with it.




  
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mwsilver
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Jul 05, 2015 09:56 |  #9

vengence wrote in post #17621193 (external link)
I'm not talking about a simple repeatable offset, if that existed I'd simply put in the MFA needed and be done with it.

You didn't mention it was inconsistent AF. That is also an occasional problem with some Sigma lenses, probably as a result of the reverse engineering because Canon does not share its AF algorithms. Often, when it does occur, the AF misses in lower light and in small target/low contrast conditions with the lens wide open.


Mark
Canon 7D2, 60D, T3i, T2i, Sigma 18-35 f/1.8, 30 f/1.4. Canon EF 70-200 L f/4 IS, EF 35 f/2 IS, EFs 10-18 STM, EFs 15-85, EFs 18-200, EF 50 f/1.8 STM, Tamron 18-270 PZD, B+W MRC CPL, Canon 320EX, Vanguard Alta Pro 254CT & SBH 250 head. RODE Stereo Videomic Pro, DXO PhotoLab, Elements 15

  
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vengence
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Jul 05, 2015 10:16 |  #10

mwsilver wrote in post #17621298 (external link)
You didn't mention it was inconsistent AF. That is also an occasional problem with some Sigma lenses, probably as a result of the reverse engineering because Canon does not share its AF algorithms. Often, when it does occur, the AF misses in lower light and in small target/low contrast conditions with the lens wide open.

Not trying to be rude, but first sentence of my post....

ordered and received a Sigma 50 Art and it had completely inconsistent focusing on my 70D when focusing through the view finder




  
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mwsilver
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Jul 05, 2015 13:01 |  #11

vengence wrote in post #17621309 (external link)
Not trying to be rude, but first sentence of my post....

Yeah, missed that.


Mark
Canon 7D2, 60D, T3i, T2i, Sigma 18-35 f/1.8, 30 f/1.4. Canon EF 70-200 L f/4 IS, EF 35 f/2 IS, EFs 10-18 STM, EFs 15-85, EFs 18-200, EF 50 f/1.8 STM, Tamron 18-270 PZD, B+W MRC CPL, Canon 320EX, Vanguard Alta Pro 254CT & SBH 250 head. RODE Stereo Videomic Pro, DXO PhotoLab, Elements 15

  
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vengence
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Jul 05, 2015 14:46 |  #12

mwsilver wrote in post #17621485 (external link)
Yeah, missed that.

No wories. ;-)a




  
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Sigma 50 Art focusing 70D vs 7dii
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